Hinges formed with thermoplastic material

ABSTRACT

Disclosed is a lid structure that includes an attachment tab connected to the lid by a living hinge. The attachment tab is configured to be attached to an external structure and the lid defines a ridge and a groove that surrounds the periphery of the lid structure except along the living hinge. Also discloses is a method of manufacturing the lid structure.

BACKGROUND

Thermoforming is a manufacturing process where a plastic sheet is heatedabove its glass transition temperature, reformed into a desired shape ina mold, cooled below the glass transition temperature, removed from themold and then trimmed to create a desired product. Twin sheetthermoforming expands on this process by bonding two separatelythermoformed sheets together prior to cooling below the glass transitiontemperature to create more complex and/or thicker products.

During thermoforming, the edges of the plastic sheet are generallyrestrained from moving while the inner portion of the sheet is stretchedand reshaped by the mold, sometimes with a differential pressure (e.g.negative vacuum pressure on the mold side of the sheet and/or positivepressure on the opposite side) pushing the sheet against the mold. Thisleaves excess material around the periphery of the molded part that isgenerally removed to create the final desired product. This excessmaterial is known as offal. Offal removal can be accomplished by placingthe molded product, including offal, in a jig configured to secure theproduct while the offal is removed by die trimming, in mold trimming,CNC cutting or machining.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front perspective view of a sectional door incorporatingmultiple panel sections.

FIG. 2 is a rear perspective view of the FIG. 1 sectional door.

FIG. 3 is a top view of a panel section of the FIG. 1 sectional door.

FIG. 4 is a side elevational view of the FIG. 3 panel section.

FIG. 5 is a front elevational view of the FIG. 3 panel section.

FIG. 6 is a bottom view of the FIG. 3 panel section.

FIG. 7 is a side cross sectional view of two panel sections joinedtogether.

FIG. 8 is an exploded side cross sectional view of FIG. 7 taken withincircle 8.

FIG. 9 is an enlarged cross sectional view of FIG. 7 taken inside circle9.

FIG. 10A is a partial view, which in combination with FIG. 10B, shows aprocess diagram detailing a method of thermoforming a panel section.

FIG. 10B is a partial view continued from FIG. 10A showing a secondportion of the process diagram detailing the method of thermoforming apanel section.

FIG. 11 is a side cross sectional view of a panel section in an asmolded configuration.

FIG. 12 is a side view of the FIG. 11 configuration.

FIG. 13 is a partial bottom view of the FIG. 6 panel section shown in anintermediate condition with offal still attached.

FIG. 14 is a partial side view of FIG. 4 taken inside circle 14.

FIG. 15 is a partial cross sectional view of FIG. 11 taken inside circle15.

FIG. 16 is a partial cross sectional view of FIG. 11 taken inside circle16.

FIG. 17 is a side cross sectional view of two panel sections joinedtogether showing flex in the living hinges during opening or closing ofthe sectional door.

FIG. 18 is a perspective view of a toolbox lid.

FIG. 19 is a top view of the FIG. 18 toolbox lid.

FIG. 20 is a back side elevational view of the FIG. 18 toolbox lid.

FIG. 21 is a bottom plan view of the FIG. 18 toolbox lid.

FIG. 22 is a front elevational view of the FIG. 18 toolbox lid.

FIG. 23 is a right side elevational view of the FIG. 18 toolbox lid.

FIG. 24 is a top plan view of the FIG. 18 toolbox lid in an intermediatestate of manufacture prior to removing the molding offal.

FIG. 25 is a partial cross sectional view of FIG. 23 taken inside circle25.

FIG. 26 is a perspective view of a box incorporating the FIG. 18 toolboxlid.

FIG. 27 is a partial perspective view of the FIG. 26 box taken insidecircle 27.

FIG. 28 is a perspective view of the FIG. 26 box showing the lid in anopen position.

FIG. 29 is an assembly view of the FIG. 26 box.

FIG. 30 is a cross sectional view of the FIG. 26 box.

DETAILED DESCRIPTION

Reference will now be made to certain embodiments and specific languagewill be used to describe the same. It will nevertheless be understoodthat no limitation of the scope of this disclosure and the claims arethereby intended, such alterations, further modifications and furtherapplications of the principles described herein being contemplated aswould normally occur to one skilled in the art to which this disclosurerelates. In several figures, where there are the same or similarelements, those elements are designated with the same or similarreference numerals.

Referring to FIGS. 1 and 2, a sectional door 50 is illustrated.Sectional door 50 includes a plurality of panel sections 52, bottompanel section 54 and top panel section 56 attached together formingsectional door 50. In this context, sectional door refers to a door thatincludes separate hinged panels that slide along a slide track or otherguide to open and close the door. Common examples include overheadgarage doors and overhead vehicle trailer doors. Sectional door 50illustrated in FIGS. 1 and 2 is configured as a vehicle trailer but thedoor described herein can be utilized for other desired doorapplications. Similarly, while overhead type doors are explicitlydescribed herein, other sectional door configurations are intended to becovered, including section doors configured for side or bottom storagewhen opened.

Panel sections 52, 54 and 56 are coupled together by attachment tab 62that is a part of panel sections 52 and 54. Details of this attachmentare discussed below.

Each of panel sections 52, 54 and 56 include recesses 64 on the rightand left side as shown in FIG. 2. Recesses 64 may be configured toaccept attachment hardware to couple sectional door 50 to guides orrollers to be used in conjunction with a track or other guide mechanismto hold sectional door 50 in position and permit opening and closingsectional door 50 as is known in the art. Bottom panel section 54 alsoincludes recesses 66 and 68. Recess 66, in the illustrated embodiment,is configured to attach a handle for opening and closing sectional door50 while recess 68 is configured to accept a latching mechanism tosecure sectional door 50 in a closed position and to provide an optionallocking mechanism. The particular configuration of recesses 64, 66 and68 is dependent upon the desired hardware to be attached to sectionaldoor 50 and can be varied or omitted as appropriate.

Section door 50 includes outer surface 58 as shown in FIG. 1 and innersurface 60 as shown in FIG. 2. The illustrated outer surface 58 issubstantially flat and is adapted to receive painting, printing and/orsignage for use in conjunction with a vehicle.

The following includes a detailed description of panel section 52. Itshould be understood that many of the features described below withregard to panel section 52 are equally applicable to bottom panelsection 54 and top panel section 56. Bottom panel section 54 and toppanel section 56 are not otherwise described.

Referring to FIGS. 3-6, panel section 52 is illustrated. Panel section52 includes attachment tab 62, panel portions 70 and 72, living hinges74 and 76, outer surface 58, inner surface 60 and ribs 80. Living hinge74 delimits attachment tab 62 and panel portion 72. Living hinge 76delimits panel portions 70 and 72. As described below, attachment tab62, panel portions 70 and 72 and living hinges 74 and 76 are integrallyformed as a monolithic structure. The top and bottom of attachment tab62 and living hinge 74 are defined by edge 88. In this context, “livinghinge” refers to a thinned, flexible plastic hinge, that both joins twoparts together and permits those parts to bend along the line of thehinge. Panel portion 52 is illustrated in a broken configuration topermit additional details to be shown. It should be understood thatpanel portion 52 has overall width 78 that is configurable to fit adesired door width. As discussed above, outer surface 58 of panelsection 52 includes a substantially flat surface conversely innersurface 60 of panel section 52 includes a plurality of ribs 80 that areoptionally included for stiffness and strength as further discussedbelow.

As best shown in FIG. 6, panel portion 70 defines receiver portion 82that is configured to receive attachment tab 62. Attachment tab 62includes a plurality of fastener holes 84 spaced along its length whilereceiver portion 82 includes a plurality of fastener holes 86 spacedalong its length mirroring the positions of fastener holes 84.Comparison of FIGS. 3 and 6 show that fastener holes 84 are throughholes while fastener holes 86 only pass through inner surface 60 but donot penetrate outer surface 58. This is discussed in additional detailbelow.

Referring now to FIGS. 7-9, two panel sections 52 are illustratedcoupled together by fastener 98. While FIGS. 7 and 9 illustrate a crosssection and thus show only a single fastener 98, it should be understoodthat a plurality of fasteners 98 are utilized to fasten panel sections52 together via fastener holes 84 and 86 as discussed above. Aspreviously discussed, each panel section 52 includes panel portions 70and 72 separated by living hinge 76 and living hinge 74 separatesattachment tab 62 from panel portion 70.

Outer surface 58 includes outer surface 94 on panel portion 70 and outersurface 96 on panel portion 72. In the illustrated cross section, panelportion 52 includes outer sheet 100, inner sheet 102, and weld seam 108.Panel portion 70 defines longitudinal axis 112 and panel portion 72defines longitudinal axis 114, outer sheet 100 defines bearing surfaces116 and 118 and recesses 120 and 122. Inner sheet 102 defines bearingsurfaces 104 and 106 and recess 110.

When assembled as sectional door 50, panel sections 52 are arranged inan abutting relationship with bearing surface 104 directly abutting andbearing against bearing surface 106. When aligned and arranged in thisway, fastener holes 84 and 86 are configured to align permittingplacement of fastener 98. As discussed above, fastener 98 can beconfigured to pass through attachment tab 62 and only inner sheet 102 tosecure the two panel sections 52 together without affecting outer sheet100.

In the illustrated embodiment, fastener 98 is a rivet type fastener thathas a blind side expander that is insertable through a hole and thenlater expanded to complete the fastener, as is well known in the art.Other embodiments (not illustrated) use other types of fasteners asdesired. For example, fastener hole 86 could include an integral nutbody, and fastener 98 could include a threaded bolt. In yet otherembodiments, attached tab 62 could be joined to receiver portion withouta mechanical fastener by welding or adhesive. In yet other embodiments(not illustrated), fastener 98 could pass through outer sheet 100. Anydesired method may be used to join panels together.

As discussed in greater detail below, in the illustrated embodiment,outer sheet 100 and inner sheet 102 are thermoformed together andinclude welded seam 108. Welded seam 108 is separated from bearingsurface 106 by recess 110 with receiver portion 82 and weld seam 108configured so that welded seam 108 does not contact bearing surface 104(or any other part of the attached panel section 52).

Referring to FIG. 9, an enlarged view proximate to living hinge 76 isillustrated. Bearing surfaces 116 and 118 are configured to abut andbear against each other when longitudinal axes 112 and 114 are alignedas illustrated. Panel portions 70 and 72 also define recesses 120 and122 that separate bearing surfaces 116 and 118 from living hinge 76.Recess 120 and 122 are configured to never contact each other.

Bearing surfaces 104, 106, 116 and 118 are configured to support andtransfer compressive loads across the illustrated abutting surfaces.

Referring now to FIG. 10, process 200 is illustrated. Process 200details many process steps that could be used to thermoform panelsection 52. However, process 200 is not all-inclusive and manyadditional steps would be apparent to a person of ordinary skill in theart. The steps described in process 200 generally involve amulti-station thermoforming machine that includes at least four stationsthat move plastic sheets between the four stations by a set of clampframes that rotate between the four positions. The four positionsinclude a load/unload station, a first preheat oven, a second final heatoven and a molding position where thermoforming takes place. Themanufacturing process described herein is related to making a singleunit. It should be understood that this manufacturing process isintended to be used as a continuous process where the actions describedfor each station repeatedly reoccur, facilitating continuous productionof manufactured parts. Furthermore, while a multi-station thermoformingmachine is described, process 200 is intended to be adapted to whatevertype of thermoforming machine is desired with appropriate modificationsto account for known differences. Similarly, process 200 is intended tobe adaptable by persons skilled in the art to other types ofmulti-station thermoforming machines that are not explicitly described,for example, thermoforming machines that clamp two sheets in a singleclamp frame, as known in the art.

In any event, process 200 begins with step 202. In step 202 inner sheet102 is loaded onto a load table in the load/unload station. In step 204the load table is moved up to bring inner sheet 102 into the boundariesof a first clamp frame and in step 206 the clamp frame clamps innersheet 102 around the periphery to secure inner sheet 102 within theclamp frame. The load table is then lowered back down to the loadposition.

Process 200 continues with step 208 where the clamp frames are rotatedmoving the first clamp frame into the preheat oven and moving a secondclamp frame into position in the load/unload station and in step 210. Instep 210 outer sheet 100 is loaded onto the load table and in step 212the load table is moved up, positioning outer sheet 100 within thesecond clamp frame. In step 214, outer sheet 100 is clamped within thesecond clamp frame and the load table is lowered.

Process 200 continues with step 216 where the clamp frames are rotatedagain, moving the first clamp frame into the final heat oven and thesecond clamp frame into the preheat oven. This is followed by step 218where the clamp frames are rotated yet again moving the first clampframe into the forming area and the second clamp frame into the finalheat oven. By this time, inner sheet 102 should be heated above itsglass transition temperature. Immediately after moving the first clampframe in the forming area, a bottom mold is moved into contact with thefirst sheet in step 220. In step 222, a vacuum assist is utilized toform inner sheet 102 to the bottom mold. After inner sheet 102 is formedto the bottom mold then inner sheet 102 is released from the first clampframe in step 224 and the bottom mold and inner sheet 102 are lowereddown in step 226.

This is followed by step 228 where the clamp frames are rotated again,moving the second clamp frame into the forming area where the top moldis lowered down into contact with outer sheet 100 in step 230 and thensubsequently vacuumed formed to conform to the shape of the top mold instep 232. Outer sheet 100 continues to be retained in the second clampafter being formed to conform to the top mold.

In step 236, the top and bottom molds are brought together bringingportions of the inner sheet 102 into contact with the outer sheet 100.This is followed by step 240 where the top and bottom molds are lockedtogether with bayonets and air bags are inflated to create a tight sealand clamp the top and bottom molds together. Next in step 242, blowneedles are extended through inner sheet 102 and pressurized as isapplied through the blow needles to the spaces between inner sheet 102and outer sheet 100. This could include slightly pressurizing the spaceand also removing hot air from the space by opening some of the needlesto atmosphere while pressurizing other vents. This could also includesequentially applying pressure through the needles at high and lowpressure while some of the needles are open to atmosphere. Generally,pressurized air is injected in approximately half of the needles whilethe remaining needles are vented to atmosphere. This creates a smallpositive pressure and an air flow that helps remove hot air capturedbetween outer sheet 100 and inner sheet 102. In other instances, highpressure air is injected to assist in forming the part against the moldsfor a portion of step 242.

This is followed by equalizing the pressure in the space between thefirst and second sheets with atmospheric pressure through the needles instep 244 to prevent ballooning or collapse of the part due todifferential pressure between the interior space and the atmosphere.This also allows any heat gradients in the space between the sheets toequalize. The blow needles are then retracted from inner sheet 102. Notethat while process 200 describes the blow needles only extending throughinner sheet 102, the blow needles can extend through any surfacedesired, including outer sheet 100.

After sheets 100 and 102 are sufficiently cooled, bonded and weldedtogether, the top and bottom molds are opened in step 245. This isfollowed by step 246 where the clamp frames are rotated, moving thesecond clamp frame into the load/unload station where, in step 247, thesecond clamp frame is opened, releasing the second sheet and formedpanel section 52 is removed. Immediately after removing the formed panelsection 52, living hinge(s) 74 and 76 are flexed in step 248. Tofacilitate this, edges 88 may optionally be die cut between the top andbottom molds in step 240. After the formed part is removed it is clampedin a jig and the offal is machined off in step 250, completing panelsection 52.

Referring now to FIGS. 11 and 12, panel section 52 is illustrated asoriented during thermoforming in process 200. (Note that FIGS. 11 and 12are rotated 90 degrees to better fit on the page.) In one manufacturingorientation, the illustrated panel section 52 would be orient in a “V”configuration, with living hinge 76 positioned below living hinge 74.

FIG. 11 illustrates a cross sectional view of panel section 52 showingmelt bonds 130 and 132 between outer sheet 100 and inner sheet 102. Meltbonds 130 are positioned at the top of ribs 80 and represents anoptional technique to stiffening panel section 52 by increasing thepoints of contact between outer sheet 100 and inner sheet 102 and byproviding increased web structures between outer sheet 100 and innersheet 102. Melt bond 132 is on the outer edge near receiver portion 82and corresponds to weld seam 108 prior to machining.

Living hinges 74 and 76 also represent a point of melt bonding betweenouter sheet 100 and inner sheet 102. However, the relative force appliedto the areas of living hinges 74 and 76 are substantially higher thanmelt bonds 130 and 132 to facilitate forming living hinges 74 and 76. Inprocess 200 this is accomplished by including a movable insert in thetop and/or bottom molds that's position can be adjusted along the lengthof living hinges 74 and 76, for example by shimming the movable insert.This permits control of the thickness of living hinges 74 and 76.

As shown in FIG. 11, longitudinal axis 112 and 114 of panel portions 70and 72 are angled apart by mold angle 134 during thermoforming. In theillustrated embodiment, mold angle 134 is equal to approximately 140°.In other embodiments (not illustrated) mold angle 134 could be betweenapproximately 130° and 150°.

As shown in FIG. 12, bearing surface 104 is angled from longitudinalaccess 112 by angle 136. In the illustrated embodiment, angle 136 isequal to approximately 70°. In other embodiments, angle 136 may be equalto approximately half of mold angle 134.

Referring to FIG. 13, a partial bottom view of panel section 52 isillustrated showing panel section 52 in an incomplete state as it mayappear after step 246 in procedure 200 but before steps 248 or 250. Asillustrated in FIG. 13, panel section 52 includes offal 140, weld seam142, vent 144, receptor 146, needle hole 148 and die cut score line 150.Offal 140 includes the portions of inner sheet 102 (and outer sheet 100which is not visible in this view but is located on the opposite side)that is gripped by the clamp frames and which provide a reservoir ofplastic material for draw down during molding. Offal 140 includes mostof weld seam 142 that defines the outer periphery of panel section 52.Vent 144 and receptor 146 are molded structures that extend into theoffal area to provide venting of the interior spaces defined byattachment tab 62. Receptor 146 is configured to receive a blow needlein step 242 of procedure 200. Vent 144 provides an internal passagewaybetween receptor 146 and the interior space between outer sheet 100 andinner sheet 102 in attachment tab 62. Needle hole 148 depicts the holewhere the blow needle extended through inner sheet 102.

Also shown in FIG. 13 is die cut score line 150 along the bottom ofattachment tab 62 and living hinge 74. Die cut score line 150 is locatedin weld seam 142 and may represent either a thinned portion of weld seam142 or a through cut. Panel section 52 shown in FIG. 13 is machined instep 250 of procedure 200 to the final configuration illustrated inFIGS. 3-6 by machining or cutting off offal 140 along weld seam 142.Vent 144 and interceptor 146 are machined or cut off and removed withthe offal.

Referring to FIG. 14, partial side view of panel section 52 isillustrated mirroring the portion of panel section 52 shown in FIG. 13.As shown in FIG. 14, machining or cutting vent 144 off leaves passage152 through the sidewall of attachment tab 62.

Referring to FIG. 15, an enlarged view of the FIG. 11 cross section ofpanel section 52 proximate to living hinge 76 is illustrated. As shownin FIG. 15, living hinge 76 includes thickness 160, bottom radius 162,top radius 164, with bearing surface 116 having a length 166 and bearingsurface 118 having length 168. In the illustrated embodiment, thickness160 is approximately equal to 0.030 inches. In other embodiments,thickness 160 can vary between approximately 0.028 and 0.040 inchesthick. In the illustrated embodiment, radiuses 162 and 164 are bothequal to approximately 0.063 inches and lengths 166 and 168 are bothequal to approximately 0.29 inches. In other embodiments, lengths 166and 168 can vary between approximately 0.10 and 0.30 inches. In theillustrated embodiment, panel width 170 is equal to approximately 1.5inches.

Referring to FIG. 16, an enlarged view of FIG. 11 proximate to livinghinge 74 is illustrated showing living hinge thickness 172, top radius176 and bottom radius 174. In the illustrated embodiment, thickness 172is approximately equal to 0.030 inches. In other embodiments, thickness172 can vary between approximately 0.028 and 0.040 inches thick. In theillustrated embodiment, radiuses 174 and 176 are both equal toapproximately 0.063.

Referring to FIG. 17, a cross sectional view of two panel sections 52 isillustrated with panel sections 52 joined together at attachment tab 62and receiver portion 82 as discussed above. The upper panel section 52is shown flexed through an approximate 90° bend as would be typical whenopening or closing most sectional doors. In particular, in the upperpanel section 52, longitudinal axes 112 and 114 are angled apart byapproximately 135° while longitudinal axis 114 on the upper panelsection 52 and longitudinal axis 112 on the lower panel section 52 arealso angled apart by approximately 135°. Bearing surfaces 116 and 118 onthe upper panel section do not bear against each other. Similarlybearing surface 106 on the upper panel section 52 does not bear againstbearing surface 104 on the lower panel section 52 (as compared to whatis illustrated in FIGS. 7-9).

Referring to FIGS. 18-23, lid 300 is illustrated. Lid 300 is a toolboxlid for a truck toolbox. Lid 300 is thermoformed from plastic sheets 302and 304 bonded together along bond flange 306. Lid 300 includes topsurface 308, bottom surface 310, body 311, tab 314 which is separatedfrom body 311 by living hinge 316. Body 311 has an internal cavity 312and tab 314 has internal cavity 313. Internal cavities 312 and 313represent the space between sheets 302 and 304 when they arethermoformed together. Tab 314 also includes a plurality of vents 317.As discussed in greater detail below, vents 317 are molded structuresthat extend into the offal area (removed in FIGS. 18-23, shown in FIG.24) to vent internal cavity 313.

As best illustrated in FIG. 21, bottom surface 310 includes a pluralityof ribs 318 that are optionally included for stiffness and strength.Ribs 318 may provide web structures across bottom surface 310 that mayserve to increase the overall strength and stiffness of bottom surface310 and body 311.

Also illustrated in FIG. 21 are a plurality of blow needle recesses 319and holes 320. Holes 320 depict the hole left when a blow needle isextended through plastic sheet 304 during a thermoforming process tovent and/or move a vent transfer fluid through internal cavity 312.

Referring now to FIG. 24, lid 300 is illustrated in an intermediatemanufacturing condition prior to removing the molding offal. Unfinishedlid 321 includes offal 322, chamber 324 and vents 326. Chamber 324 isdefined in the offal region of plastic sheets 302 and 304 and is boundby bond flange 306. Vent 326 is also defined by plastic sheets 302 and304. Vent 326 connects the interior space of chamber 324 with internalcavity 313 in tab 314. Chamber 324 is configured and arranged to receiveone or more blow needles during the molding process. The blow needlescan then be used to vent internal cavity 313 and/or move a vent transferfluid, such as air, through vents 326 and internal cavity 313 to aide incooling plastic sheets 302 and 304 defining tab 114.

As best shown in FIG. 23, tab 314 is dimensionally configured too smallto reliably insert blow needles into internal cavity 313. Chamber 324provides a structure that is sufficiently large to receive a blow needleand vents 326 fluidly connect the two. In one embodiment, an individualchamber 324 can receive blow needles proximate to each vent 326. In oneembodiment, some blow needles can provide a supply of heat transferfluid while the remaining blow needles can withdraw the heat transferfluid to provide a flow through internal cavity 313. In otherembodiments, the central chamber 324 illustrated in FIG. 24 couldreceive one set of blow needles that supply heat transfer fluid whilethe two chambers 324 positioned on the outside could receive blowneedles to withdraw the heat transfer fluid to provide a flow throughinternal cavity 313.

Referring now to FIGS. 26-30, box 400 is illustrated. Box 400illustrates one application of lid 300 where lid 300 is coupled to anexternal structure to complete box 400. Box 400 includes lid 300, base402, front panel 404, side panels 406, back panel 408 and spring 410.Back panel 408 also includes channel 112 constructed to receive tab 314to couple lid 300 to back panel 408 and box 400. In the illustratedconfiguration, channel 412 receives tab 314 by sliding tab 314longitudinally along the length of channel 412. A plurality of fasteners414 optionally longitudinally secure tab 314 in channel 412 by passingthrough both channel 412 and tab 314. In the illustrated configuration,box 400 is configured as a truck bed toolbox mountable in a truck bedbetween bed side rails. However, box 400 could be configured as desiredfor a other applications.

Hinge 316 on lid 300 may have resiliency sufficient to support theweight of lid 300 when tab 314 is coupled to channel 412 to the extentthat lid 300 does not close into contact with front panel 414 without anadditional downward force applied to lid 300 (when oriented as shown inFIGS. 26-28). Spring 410 may optionally be added to bias lid 300 upwardsto maintain lid 300 in an open position unless a closing force isapplied to lid 300 sufficient to overcome spring 410 and the resiliencyof hinge 316 to close lid 300 into contact with front panel 404. Alatching or locking feature may be optionally included to maintain lid300 in a closed position.

This disclosure serves to illustrate and describe the claimed inventionto aid in the interpretation of the claims. However, this disclosure isnot restrictive in character because not every embodiment covered by theclaims is necessarily illustrated and described. All changes andmodifications that come within the scope of the claims are desired to beprotected, not just those embodiments explicitly described.

We claim:
 1. A method of manufacturing a part, the method comprising:heating a first plastic sheet above a glass transition temperature;heating a second plastic sheet above the glass transition temperature;molding the first plastic sheet with a first mold; molding the secondplastic sheet with a second mold; and impressing the first plastic sheetand the second plastic sheet together between the first and second moldsthereby forming the part and a living hinge on the part, wherein theliving hinge is between approximately 0.028 inches and approximately0.040 inches thick.
 2. The method of claim 1 further comprising flexingthe living hinge before the part has cooled to an ambient temperature.3. The method of claim 1, wherein the part includes an elongatedstructure and a tab, wherein the living hinge separates the elongatedstructure and the tab and wherein the tab is constructed and arranged tobe coupled to an external structure.
 4. The method of claim 3 whereinthe tab is constructed and arranged to slide within a channel.
 5. Themethod of claim 3 wherein the tab is constructed and arranged to receivea plurality of mechanical fasteners to couple the tab to the externalstructure.
 6. The method of claim 1, further comprising: whilecompressing the first and second sheets, die cutting the first andsecond sheets on both ends of the living hinge.
 7. The method of claim1, wherein the elongated structure has a width and wherein the livinghinge is continuous and extends across substantially the entire width.8. The method of claim 1, wherein the living hinge is constructed andarranged to flex no more than ninety degrees.
 9. The method of claim 3,wherein the living hinge has a resiliency sufficient to support theweight of the elongated structure with the weight of the elongatedstructure deflecting the living hinge less than 80 degrees.
 10. Anapparatus comprising: a first sheet and a second sheet thermoformedtogether defining a lid structure, an attachment tab and a living hingeunitarily formed between the lid structure and the attachment tab,wherein the lid structure defines an inside ridge, an outside ridge anda groove between the inside and outside ridges, wherein the inside ridgeand the groove are in the margin of the lid structure and substantiallysurround the lid structure, wherein the outside ridge is proximate tothe periphery of the lid structure except along the living hinge andwherein the tab is constructed and arranged to be coupled to an externalstructure.
 11. The apparatus of claim 10, wherein the living hinge isbetween approximately 0.028 inches and approximately 0.040 inches thick.12. The apparatus of claim 10, wherein the tab is constructed andarranged to slide within and be received in a channel.
 13. The apparatusof claim 10, wherein the tab is constructed and arranged to receive aplurality of mechanical fasteners to couple the tab to the externalstructure.
 14. The apparatus of claim 10, wherein the lid structure hasa width and wherein the living hinge is continuous and extends acrosssubstantially the entire width.
 15. The apparatus of claim 10, whereinthe living hinge is constructed and arranged to flex no more than 90degrees.
 16. The apparatus of claim 10, wherein the living hinge has aresiliency sufficient to support the weight of the lid structure withthe weight of the lid structure deflecting the living hinge less than 80degrees.
 17. A lid comprising: a first sheet and a second sheetthermoformed together defining a lid structure, an attachment tab and aliving hinge unitarily formed between the lid structure and theattachment tab, wherein the attachment tab is constructed and arrangedto slide within and be received in an extruded metal channel, whereinthe living hinge is between approximately 0.028 inches and approximately0.040 inches thick, wherein the living hinge is continuous and extendsacross substantially an entire width of the lid structure and whereinthe living hinge has a resiliency sufficient to support the weight ofthe lid structure with the weight of the lid structure deflecting theliving hinge less than 80 degrees.
 18. The lid of claim 17, wherein theliving hinge is constructed and arranged to flex no more than 90degrees.
 19. The lid of claim 17, wherein the living hinge isapproximately 0.030 inches thick.